Controllable pitch change mechanism for dual rotation propellers



Nov. 20, 1945. H. M. M COY CONTROLLABLE PITCH CHANGE MECHANISM FOR DUAL ROTATION PROPELLERS Filed Sept. 11, 1942 5 Sheets-Sheet 1 [N VE N TOE flow/m0 M. M Gov H. M. MccoY Nov. 20, 1945.

2,389,161 CONTROLLABLE PITCH CHANGE MECHANISM FOR DUAL ROTATION PHOPELLERS 5 Sheets-Sheet 2 Filed Sept. 11, 1942 INVENTOFE How/v20 M. Ma CY CONTROLLABLE PITCH CHANGE MECHANISM FOR DUAL ROTATION PROPELLERS Filed Sept. 11, 1942 5 Sheets-Sheet 3 Nov. 20, 1945. H. M. MCCOY 2,389,161

IN VE N TOR How/n20 M.- Mc OY ATTORN Mm 4 l 9 a 8 h Q. 2 a .m S 5 H; M. M COY CONTROLLABLE PITCH CHANGE MECHANISM FOR DUAL ROTATION PROPELLERS Filed Sept. 11, 1942 Nov. 20, 1945.

I v INVENTO HOWARD M. No Cov Bu d fi -uv ATT Nevis 1 Nov. 20, 1945. H. M. M coY CONTROLLABLE PITCH CHANGE MECHANISM FOR DUAL ROTATION PROPELLERS Filed Sept 11, 1942 5 Sheets-Sheet 5 INVENTOB /7o WARD M. Ma

-M {"I/ I ATT NEY6 Federated Nov. 1945 r V 4 CONTROILABLE PITCH CHANGE MECHA- NISM son nUAL no'm'non PBOPELLEBS Howard M. McCoy, ran-sel om Application September 11, 1942, Serial No. 458,ii39

- 14 Claims. (Cl. I'm-435.6)

(Granted under the act of March 3, 1883, as

amended April 30, 1928: 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to dual-rotation propellers and more particularly to mechanism for controlling the pitch of the blades of both of the propellers simultaneously.

By dual-rotation" is commonly meant a pair of oppositely rotating propellers operating in close tandem, mounted on concentric shafts and rotating at equal speeds. I

Mechanism for accomplishing this purpose as heretofore proposed is complicated and costly,

and it is therefore an object of this invention to provide a device which will have less parts and therefore be of lighter weight and greater simpiicity.

It has been found that, in a device of this character, it is advantageous, in order to cancel propeller torque effects, to have an arbitrary and variable diderential pitch setting between the front and rear propeller blades. For small angle pitch settings used at take-off and low forward velocities there should be but very little if any difference between the pitch of the front and the pitch of the rear blades. At high forward velocities there should be several degrees did'erence with the setting of the rear propeller lower than that of the front. It is desirable to have the pitch difierential vary directly between the small differential at low velocities to the large difierential at high velocities. It is therefore an object of this invention to so construct and arrange the mechanism that this advantage may be had.

Other objects and advantages will be disclosed as the invention is described in detail and reference is had to the drawings, wherein,

Fig. 1 is a more or less schematic view of a pitch-changing mechanism as applied to a dualrotation propeller installation.

Fig. 2 is a view similar to Fig. 1, but with a different type of gearing.

Fig. 3 is a transverse section taken at 3-3 of Fig. 1 through the pinion carrier and pinions.

Fig. 4 is a transverse section taken at 8-4 of Fig. 2 through the pinion carrier and pinions.

Fig. 5 is a transverse section taken at 5-5 of Fig. 1 through the pitch-changing gearing of one 5 propeller.

Fig. 6 is a transverse section taken at 5-4 of Fig. 1, through the control gearing.

Fig. 7 is a transverse section, taken at |'l of Fig. 2 through the modified form of control gearing.

I Fig. 8 is a fragmentary section taken at 8-8 of iFig. 2 through the pinions of the carrier gear- Fig. 9 is a fragmentary section, taken at 9-9 of Fig. 2 through the reversing pinions of the control gearing. 4

Fig. 10 shows a'pitch indicator mecha, pitch limit switches, and electric control means, all applicable to the structure shown in Fig. 2.

Referring more particularly to Fig. 1 an englue shaft it! has aihxed thereto two gears l2 and it. A propeller shaft is is powered-by the engineshaft through gears l2 and 2b.

Freely rotatable on the propeller shaft It is a slee /e 22, this sleeve being powered by the engine. shaft through gears it and 25, and an idler gear vM5 which is inserted between gears iii and 26, to cause reverse rotation of the sleeve with respect to the shaft. The ratio of the gears l2 and 2B equals the ratio of the gears it, at and 26, whereby the shaft l6 and sleeve 22- rotate at equal speeds. The shaft I6 is rotatable in the sleeve 22 and the sleeve is rotatable in a bearing of the casing 8!.

. 'able in combination thrust and radial bearings 42. Bearings 42 extend laterally fromthe rear hub 38 and are conventionally contained therein. The section of Fig. 1 is so broken that the blade 34 which is shown is that one which extends from the hub toward the observer and is therefore shown in phantom, while the blade is that one which extends from the hub away from the observer and is therefore shown in dotted outline.

Coaxlally adjacent bevel gears 44 and 46 are drivably secured to the hub 32 and hub 38 respectively, whereby the front propeller hub 82,

the shaft I6 and the bevel gear 54 are permanently Joined for unitary rotation, rotation preferably being in the direction of the arrow 45. The rear propeller hub 38, the sleeve 22 and the bevel gear 46 are also joined together to rotate as one part, but, due to the inclusion of the idler gear 26, are caused to rotate in the opposite direction, 1. e. in the direction of the arrow 41.

A bevel pinion carrier ring 48 surrounds the bevel gears 44 and 46, the ring being provided, at circumferentially spaced intervals, with radially extending studs 56 which may preferably be pressed fitted or otherwise fixed in the ring. Bevel pinions 52 are freely rotatable on the inner ends of the studs 58, the pinions being so held by the studs as to be properly meshed with both bevel gears 44 and 46. Obviously, with the two bevel gears 44 and 46 rotating oppositely at the same speed, the'bevel pinions 52, studs 56 and carrier ring 48 are held as a unit against rotation about the axis of the shaft l6 and sleeve 22. It should be noted that, with rotating parts completely surrounding it, there is no nonrotative part to which the carrier ring 48 could be attached to hold it against rotation. The gearing 44, 46 and 52-, which together hold the carrier ring 48 nonrotative, may conveniently be referred to as the carrier retaining gears.

Formed in the periphery of the carrier ring 48 are two axially spaced apart ballraces 54. Surrounding the ring 48 are separate rings 56 and 58, each of which has a complementary ball race 66 formed in its inner surface. With balls 51 properly placed in the races 54 and 66 the rings 56 and 58 are concentrically supported on and freely rotatable about the nonrotatable ring .48. Rings 56 and 58 have integral bevel gears 62 and 64 formed on their interfacing edges, and bevel pinions 66 are in mesh with both bevel gears 62 and 64, these pinions being each rotatable on an outwardly projecting portion 68 of a stud 56, where'- by, when one of the rings 56 or 58 rotates in one direction, the other must rotate in the opposite direction, or. to put it another way, when the ring 56 rotates in unison with the front hub 32, the ring 58 must rotate in unison with the rear hub 38. In addition to the bevel gears 62 and 64, the external spur gears I6 and I2 are formed respectively on the peripheries of rings 56 and 58. Since the gears 62, 64, 66, I6 and I2 together provide a means of connecting the two sets of propeller gears so that one may not change pitch without changing the pitch of the other, these gears may preferably be called the pitch-change connecting gears.

It should here be noted that the statement that the carrier is nonrotative is true only if the hubs 32 and 38 rotate oppositely at equal speeds and the gears 44 and 46 have exactly the same number of teeth.

If the hubs 32 and 38 rotate at difierent speeds, the carrier also will rotate, its rotations being the algebraic sum of the rotations of the two hubs. But this will cause no pitch change in the propeller blades for the reason that the rotations of the carrier relate back to the gears 56 and 58, leaving each rotate in unison with its hub 32 or 38.

Similarly, with equal propeller speeds, it may be found effective to break up vibrations to make a difference of one or two teeth between gears 44 and 46, in which case the carrier would rotate slowly, then if the same difference was provided between the teeth of gears 56 and 58; no pitch change would occur, because gears 56 and 58 would then rotate in unison each with its hub.

Rotatable on bearing surfaces formed in the rear end of the rear hub 34 are an internally toothed ring gear'14 and an externally toothed ring gear 16. The worm hafts I8 are each rotatable in (see Fig. 6) Intermediate of the ends, the shafts 18 each carry a worm 88 which is meshed with -a worm wheel 88. The worm wheels 88 are secured to the roots H of the blades 48. The ring gears 14 and I8 may conveniently be referred to as the control gears since when either is retarded the pinion 86 reacts on the retarded gear to turn the pitch-changing gearing 88-86 and I68--I62.

A second pair of worm shafts 82 are-each rotatable in bearings 84 and 86, formed in the front propeller hub. 32, eachshaft carrying, at one end. a pinion 88 which is meshed with the external spur gear I6. Intermediate of the ends, the shafts 82 each carry a worm I86 which i meshed with a worm wheel I62 carried on the inner ends of the roots 33 of the blades 84 Obviously, as long as the ring gears 14 and I8 both rotate in perfect unison with the rear hub 38, no rotation of the'shafts 18 in their bearings 86 and may take place, although they will revolve about the axis of the propeller shaft I8, and the ring 58 will be rotated in unison with the rear hub 38, the ring being dragged around by the nonrotating pinion 84 which is meshed with the spur gear teeth I2.

Since the ring 56 is connected to the ring '88 .through the bevel pinions 66, the ring 56 must rotate oppositely at the same speed and will therefore be rotating in unison with the front hub 32. Neither of the worms 88 or I 66 rotate relative to their respective worm wheels 88 or I62 and no pitch change of the blades of either propeller can take place.

However, should one of the ring gears 14 or -I6 be held against rotation, or be retarded in its rotation with respect to the rear hub 38, the shafts I8 will be rotated in their hearings in one direction and, since driving through the bevel plnions 66 reverses the direction, the shafts 82 will be rotated in their bearingsin the other direction, the rotation of these shafts being operative to turn the worms 88 and I66 and their respective wheels 86 and I62 to respectively change the pitch of the blades 46 and 34. Pitch change may therefore be made in the blades of the front and rear propellers simultaneously in one or the other direction by braking one or the othe of the ring gears 14 or I6. By making the worm gear sets 88-86 and the worm gear sets I66-I 62 all righthand, the retarding of the internal ring gear 14 will decrease the pitch of both propellers, while the retarding of the external gear l6.will increase their pitch. To facilitate description, the group of gears 84, 86, 88 -and 86, as well as the group 88, I66 and I62, may hereinafter be referred to as the pitch-changing ears. While any form of brake will operate to change the pitch, a specific example is. included in order to show a complete operative structure.

The hydraulic braking mechanism shown is of the type wherein gear or vane pumps are driven against substantially zero head by the members which are to be braked, with means for restricting one or the other pump outlet and thus increasing the head or resistance against which that pump operates until the torque of the member driving the pump is overcome and it is retarded or stopped.

It will, of course, be understood that the pump braking torque on one ring gear is equalto the resistance of the propellers to pitch increase, while the pump braking torque on the other ring gear is equal to the resistance of the propellers to pitch decrease. This latter is a relatively small torque because of the natural depitching tendency of the blades, due to the negative centrifugal pitch moments. The pumps must therefore have braking capacity to overcome this resistance. Since the internally toothed ring gear M is of larger pitch diameter than the externally toothed ring gear 16, it follows that the speed of pitch change, in the structure shown in Fig. 1, may ordinarily be faster in one direction than in theother. It may, however, be made approximately equal by properselection of gears and pump capacities. i v

The pump driving shafts I01 and I06 are rotatable in bearings I08 and I I in the casing 3|. and

' are so positioned in 'the casing that the pinion hub 38, the pitch of the front propeller should normally be slightly greater than the rear. This is readily accomplished in the mechanism herein H2, which is secured to the end of the shaft I04,- I

is in mesh with the internal ring gear 14, and. so that the pinion H8, whichis secured to the end of the shaft I08, is in mesh with they external ring gear it.

The pumps H5 and IIi are of conventional ty and are arranged to pump through continuous circuits H9 and I'll which may be closed or restricted, each by one or more valves. In the embodiment shown, a single plunger valve I21 controls both circuits, and an engine-driven centrifugal governor I29 controls the plunger valve, the valve being brought to a central or neutral position by the governor when the governor is being rotated at the desired speed, and in this neutral position both pump circuits are open and no change in pitch is therefore being effected. Adjustment of the governor spring tension to obtain variable governing-speeds may be made in the conventional manner.

Overspeed of the engine-driven governor I28 will, of course, close or partly close the circuit II 9 which will retard the pump H5 which willln turn retard the internally toothed ring gear 18. Any reduction in speed of the ring gear 14 below that of the hub 38 will roll the pinion 86 and worm. 88 rearwardly with respect to the hub 38 (clockwise viewed from the right) which, through the gearing as, 12, st, as, 52 and it, will turn the pinion 38 and worm I88 forwardly with respect to unitary rotation, but due to the fact hat the the hub 32 (anticlockwise viewed from the right),

whereby the pitch of the blades of both propellers will be increased, and the engine thereby brought back to the selected speed.

Conversely, underspeed of the engine will close or partially close the circuit I2I which will retard the pump ill, which will in turn retard the externally toothed ring gear 16. Any reduction in speed of the ring gear 16 below that of the hub 38 will roll the pinion 88 and worm 88 forwardly with respect to the hub 38 (anticlockwise viewed from the right) which, through the same gearing 84, 72, 54, B8, 62 and '10, will turn the pinion 98 and worm I00 rearwardly with respect to the hub 32 (clockwise viewed from the right), whereby the pitch of the blades of both propellers will be decreased, and the engine thereby broughtback up to the selected speed. Bypass channels I23 and I 25 having relief valves I3I and Bare provided in the circuits H3 and I2I for relieving the circuits of excess pressure which may result from a complete closing of either of them by the valve I21.

- As hereinbefore discussed, due to the influence of the front propeller slip stream on the rear prostantially the same in function, it diflers considerably from that shown in Fig. 1 in structural details, the carrier retaining gears and the propeller connecting gears being spur instead of bevel, and the pitch-changing mechanism being operated by a reversible electric motor instead of braking one or the other of a pair of reaction gears for this purpose.

The propeller shaft H6 and the propeller sleeve II8 rotate oppositely. The means for causing opposite rotation isnot shown, but it may comprise an arrangement of gears such as I2, I l, 20, 24 and 20 of Fig. 1.

Affixed'to the front end of the shaft H6 is the front propeller hub I20. Hub I20 carries the blades I22 which have their roots I24 rotatable in combined thrust and radial bearings I 26. Bearings I26 extend laterally from the front hub I20 and are conventionally contained therein.

Affixed to the sleeve I I8 is the rear propeller hub I28. Hub I 28 carries the blades I30 which have their roots I32 rotatable in combined thrust and radial bearings I34. Bearings I36 extend laterally from the rear hub I28 and are conventionally contained therein.

Coaxial spur gears I36 and I38 are amxed to the shaft IIS and sleeve II8 respectively, whereby the front propeller hub I20, shaft IIS and gear I36 rotate in'unison, preferably in the di rection of the arrow I35. The rear propeller hub I28, sleeve H8 and gear I38 are also joined for sleeve may be driven through an idler gear (not shown) the rear hub and its associated parts may rotate oppositely from those of the front hub, preferably at. equal speedsyand preferably in the direction of the arrow I37.

A pinion carrier I40 consists of a relatively thick disc placed between externally toothed gears I36' and I38 and rotatably carried on the shaft I I6 of any other suitable bearing support which is concentric with the axis of rotation.

Pairs of cup-shaped pockets I39 are formed in the faces of the carrier disc I40 for planet pinions (see Figs. 4 and 8), each pocket having sufficient thickness MI left at the bottom to support a stud I42 upon which the pinion may ro-' The two pockets of a pair are formed in tate. the disc on opposite sides thereof and at such distance apart that the pockets of apair run into each other and the pinions of a pair are in mesh one with the other (see Fig. 8). The pinions are of 'wide enough face to overlap each other in driving relation and also extend from the pockets in the disc to overlap the faces of the gears I36 and I38. i I

Six pairs of pinions will provide a satisfactory arrangement, three'pairs I being radially p0- sitioned to mesh with the gears I36 and I38, and the other three pairs I" be ng radially further from the axis of rotation so as to be out of mesh tative with respect to the axis, and, with the car:

rier nonrotative with respect to the axis, the rotation of one of the internally toothed gears I48 or I50 will rotate the other oppositely, that is,

when the ring gear I48 rotates in unison with the front hub I20, the ring gear I50 rotates in unison with the rear hub I28, and this condition maintains except when pitch changing is being effected.

The statement that the carrier I40 will be nonrotative is, as has already been explained relative to Fig. 1, based on the assumption that the two hubs I20 and I28 rotate oppositely at the same speed and that the internal gears I48 and I50 have the same number of teeth. Where there is a difference between the speeds of the two hubs I20 and I28 or in the number of teeth in gears I36-I 38 and in I48-I50 the carrier will rotate slightly without, however, affecting the pitch change.

For effecting pitch changes, externally toothed gears I53 and I55 are formed on the peripheries of the gears I48 and I50. Gears I53 and I55 are in mesh with two pinions I56 and two pinions I58 which are secured to or integral with the righthand worms I60 and I62.

axis of shaft II6 without rotating on its own Worms I60 have rotative bearing in bearing I bosses I64 and I66 and are meshed with worm wheels I68 on the inner ends of the front propeller blade roots, while worms I62 have rotative bearing-in bearing bosses I10 and I12 and are meshed with worm wheels I14 on the inner ends of the rear propeller blade roots. The shaft of the worm I62 extends through the rear wall of the propeller hub I28 and has attached to its rear end, the pinion I16. As long as the pinion I16 revolves ab ut the axis of the shaft I I6 without rotating on its own axis, no change in propeller pitch will take place. But when pinion I16 rotates on its own axis, forward or backward, whether or not it revolves about the axis of the shaft II6, a change in propeller pitch will take place. The mechanism for rotating the pinion I16 On its own axis, whether or not it is at the time revolving about the axis of the shaft I I6, is

axis, the bevel gear I80 will revolve one turn for each turn of the hub I28. In order then to allow the bevel pinion I84 to rotate on its own shaft I86 without revolving around the axis of the shaft I I6, the bevel gear I82 must be rotated oppositely from the bevel gear I80 and at the same speed.

To provide this opposite rotation, the bevel gear 182 has attached thereto, or integral therewith. a spur gear 200, while the tube I18 carries a similar spur gear 202. these gears being connected by pairs of overlapping pinions 204 idling on studs 206 extending from the rear wall of the casing I18.

Because of the pairs of overlapping pinions 204, the gear 202 drives the spur gear 200 and the bevel gear I82 backwardly while the bevel 'gear I60 rotates at the same speed forwardly, the bevel pinions being rotated on their own axes'but not revolved around the axis of shaft II6. Under this condition there is substantially no effort to turn the motor I96 either direction. Conversely, the pinion I 16 whose rotation on its own axis is responsible for propeller blade angle adiustment, will rotate on its own axis, in one or the other direction, whenever the motor I96 rotates and not otherwise, whereby blade adjustment takes place by motor rotation irrespective of whether the hubs I 20 and I28 are rotating or are stationary. In this respect it differs from the structure shown in Fig. 1, the braking means of which is operative only to effect blade adjustment when the propellers are under rotation, no means being provided in the structure of Fig. 1 for changing pitch shown in the stationary casing I18 which is nor-- mally attached to a part of the engine nose as at I19.

Within the casing I18 and freely rotatable on the tube I I8 are a pair of bevel gears I80 and I82 operatively connected together by bevel pinions I84. Pinions I84 are rotatably mounted on studs I86 which are circumferentially spaced apart in a ring I88. The ring I88 has an external gear I90 formed about its periphery. A pinion I92 meshes with gear I90, the shaft I94 of the pinion having rotative bearing in the rear wall of the casing I18. A reversible motor I96, including suflicient additional reduction gearing, is provided for rotating the shaft I94 forwardly or rearwardly as desired A brake, I99, preferably spring applied, is provided for holding the motor nonrotative when no current is passing through it, a solenoid brake release means being connected when the propellers are not rotating. To provide such a means for the structure of Fig. 1, the pinion .192 of Fig. 2 could be meshed with either of the ring gears 14 or 16 of Fig. 1, with the exception that element I99 would additionally have incorporated therein a solenoid-energized clutch to release the motor I96 from engagement with shaft 194 when the shaft was being turned otherwise than by the motor.

The switch mechanism for operating the motor I96 in either direction may consist of a two-position switch operable manually or by conventional governing means as is now common practice, or a combined manual and automatic control for the motor I96 may be provided as shown in Fig. 10 which includes switches for limiting the extent of pitch change either in manual or in automatic control, together with pitch-indicating mechamsm.

To apply the control means of Fig. 10 to the device shown in Fig. 2, a pinion I9I, Fig. 2, is meshed with the gear I90, the pinion shaft I88 having rotative bearing in the rear wall of the casing I18, a portion of the shaft which extends rearwardly from the casing being provided with threads I (see Fig. 10).

Since the number of turns which the motor I86 has made clockwise or anticlockwise from 9, neutral position (viewed from the right) determines the extent of pitch decrease or increase respectively of the propellers, it follows that the turns which the screw I95 makes clockwise or anti-' I -a,ase,1o1 .sisting of a carriage 288, internally threaded to fit the screw III, which may have a pointer 2l8 integral, with pitch indicia 2l2 adJacent, but may preferably have some form of indicator located more conveniently for the pilot, operative by flexible shaft or other power transmission from the the engine to respectively decrease or increase 7 its speed, and ii at any time the engine is far enough under'speed to cause the g vernor 218 to close the contacts 224-222 for pitch decrease, and ii for anyreason the engine fails to respond and increase its speed upon continued decrease inpropeller pitch, and operation of the electric motor I08 therefore continues in the direction which decreases the pitch until the pitch indicator carriage 208 opens the limit switch 240, the electric circuit will be broken,

- from zero pitch, and automatic pitch change op-' eration will not thereafter be resumed until the from a selected normal to move the two lnsulatedly spaced-apart contact members 220 and 222 upward or downward into engagementwith an intermediate stationary contact member 224. The governor may be driven by the aircraft engine through searing 228. The flyballs are held against the action of centrifugal force by a spring 228 which may be adjusted by the screw 230 or by some remote control for altering the selected normal. The arrangement oi the flyballs is such that an increase in rotative speed lowers the contact 220 into engagement with the contact 224 while a decrease in speed raises the contact 222 into engagement with the contact 224.

The manually operable switch 2 l 8 is closable on a contact 232 to provide a circuit for automatic operation of the motor I88, to an "of!" position 234, on a contact 238 for manually increasing the propeller pitch, and on a contact 238 for manually decreasing the propeller pitch. Control is through thereversible motor I08 wh'ether it is by manual or by automatic switch means.

The pitch indicator carriage 208 is so formedand positioned that its movement on the screw i08 will operate a pair of electric switches 240 and 242 for limiting the degree of propeller pitch adjustment which may be eflected by automatic operation and a second pair 244 and 246 forlirniting the degree of propeller pitch adjustment which may be eflected bymanual operation. The switches 240, 242, 244 and 248 are placedin the line of travel oi. the carriage 208 so as to be Opened thereby.

The electric motor "8 is reversible because of the inclusion of field windings 248 and 250 of op- .posite polarity, the coil 248 being employed for rotation in one direction and the coil '250for rotation in the other direction, the direction 01' the current in the armature circuit 282 remaining the same in both cases.

If the circuits are wired as in l-ig. 10 and the manual switch U6 is closed on the automatic contact 232, alternate circuits will be made upon change in governor speed, one from a battery 254 whereupon pitch decrease will stop at the predetermined minimum pitch point for which the limit switch 240 has been set, which, for example, may preferably be about fifteen degrees engine does regain suilicient speed to cause the governor HR to close the contacts 220-224,

thereby-completing a circuit through the-stillclosed bomb switch 242 which operates the motor I08 to again increase the pitch.

On the other hand, it the engine is sufllciently overspeed to have closed the contacts 220-224 for pitch increase, and if for any reason the engine fails to decrease its speed upon continued increase in propeller pitch, and operation of the electric motor I08 therefore continues in the direction which increases the pitch until the pitch indicator carriage .208 opens the limit switch 242, the electric circuit will be broken, whereupon pitch increase will stop at the prede- --tain a constant engine speed, the more extensive changes in pitch, 1. e., the feathering-and the braking positions, being effected by means of the manual switch 2 l 8. Y I

Where featherin becomes advisable, as where one of a group of engines of a large craft becomes incapacitated or 'jammed, the manual switch M8 is closed on to the contact point 238 for increased pitch, and left closed until the pitch-change carriage 208 opens the switch 246,

which may preferably be when' the pitch apthrough switch m. contacts 224 and no, limit" switch 242, field coil 250, armature 252 and back to the battery, the other from battery 254 through switch 2N, contact 224 and 222, limit switch 240, fleld'coil 248, armature 252 and back to the battery.

Current, therefore, when directed by the governor am through the one circuit, operates the motor 820 in one direction for pitch increase, and, when directed through the other circuit, operates the motor in the other direction for pitch decrease. The object of increasing or 'decreasing the propeller pitch is, or course, to cause proaches ninety degrees above zero.

For propeller braking, the manual switch 2"; is closed on to the contact point 238 for decreased pitch and usually left closed until the pitch-change carriage 208 opens the switch 244 which may preferably be when the pitch is about minus twenty-five degrees.

The combination of automatic and manual control system has the further advantage that at any time the operator may shift out of automatic control by moving the switch 2l8 from the auto matic position 232 to the of! position 234 and the pitch will be fixed at the angle shown by the pitch indicator at the time of the shift. The operator may henceforth control the pitch setting manually by momentarily holding the switch. 2l6 closed on one or the other of the points 238 or 238 as the case may require, the pitch indicator Showing him the degree of pitch change being eflected, and the switches :44 and 246 being operative to stop pitch'change if the switch is held closed for too long a period. The mechanical stops'of common practice used for limiting pitch change may supplement the limit switches as an added safety feature inasmuch as no damage can result from turning the blades to a positive stop. since the relief valves 84-88 of Fig. 2 will yield when a preselected effort is exerted at turning the propeller blades.

Since it is desirable to provide a slightly higher pitch-change ratio in one propeller than in the other, the ratio of the pitch-changing gearing on one side of the carrier may preferably be made slightly different from that on the other side as explained relative to Fig.1.

Having described severalembodiments of my invention, I claim:

1. In a dual-rotation propeller mechanism having two adjacent concentric tandem contrarotating propeller hubs with a plurality of propeller blades in each hub having their roots rotatable in hearings in the hubs, mechanism for simultaneously rotating the roots to alter the pitch of the blades, said mechanism comprising a pair oi. axially spaced gears, one secured to each hub for unitary rotation therewith, a second pair o! axially spaced gears surrounding the fist pair being overlapped and intermeshed in driving relation one with the other, the remaining portions being extended axially and intermeshed. one with each external gear, a second pair of pinions constructed and mounted substantially like the first said set except that their extended ends are intermeshed, one with each internal gear, a gear train connecting each internal gear to a propeller blade, and means for applying rotation to one 01 said trains.

3. In an aircraft propeller mechanism having two adjacent, coaxial, tandem, contrarotating, propeller hubs with a plurality of propelle blades in each hub having their roots rotatable iri'bearings in said hubs, mechanism for simultaneously rotating the roots to alter the pitch of the blades, said mechanism comprising an external spur gear on each hub secured to rotate therewith, a concentric internal spur gear freely rotatable about each external spur gear, one external spur gear and one internal spur gear constituting a pair of gears, a pinion carrier between said pairs of gears, a pair of spur pinions rotatable about their axes on said carrier, 9. portion of the faces of said spur pinions overlapping and meshing with each other, the remaining portions being extended laterally beyond the carrier and meshed, one with each external spur gear, a second pair of spur pinions substantially like the first except located radially further from the propeller axis on the carrier and meshed one with each of said intemai spur gears, and a rotation-transmitting means operatively connecting said internal spur gears to 4 the roots of said blades.

sitely, irrespective of the rotation of the first pair, 7

a set of normally nonrotating pitch-changing gearing in each hub, each set including a gear on each root, said sets operatively connecting the axially spaced gears of the second pair to the blades of the propellers, whereby the pitch of both propellers is changed simultaneously, and means for rotating the pitch-changing gearing which includes a third pair of axially spaced gears, gearing connecting one of the gears of the third pair to one of the sets of normally non-rotative pitch-changing gearing, whereby said one gear oi the third pair is rotated in rear propeller direction at propeller speed, reversing gearing connecting the other one of the gears of the third pair to the rear propeller hub, whereby the two gears oi the third set rotate oppositely, a second pinion carrier intermediate the gears of the third pair, reversing pinion means on said carrier connecting the two spaced gears of the third pair whereby the oppositely rotating gears of the pair cause said second carrier to remain non-rotative, a power source, and gearing connecting said second carrier and said power source.

2. In an aircraft propeller mechanism having two adjacent, coaxial, tandem, contrarotating, propeller hubs with a plurality of propeller blades in each hub having their roots rotatable in bearings in said hubs, mechanism for simultaneously rotating the roots to alter the pitch of the blades, said mechanism comprising a pair of external spur gears slightly spaced apart axially, one secured to each said hub for unitary rotation therewith, a pair of internal spur gears surrounding the said external gears, a pinion carrier between the two said pairs of gears, a pair of pinions mounted on, and rotatable about their axes on,

said carrier, a portion or the faces of said pinions 4. In an aircraft propeller structure wherein a propeller hub has a plurality of propeller blades with their roots rotatable in bearings in said hub, and gear trains normally nonrotative with respect to said hub for simultaneously rotating said 40 roots, mechanism for operating said gear trains which comprises a pair of axially spaced gears both coaxial with said hub, gearing connecting one of the said coaxial gears to the normally nonrotating gears of said gea trains, gearing including a reverse idler pinion set connecting the other of said coaxial gears to the propeller hub, whereby the two coaxial axially spaced gears rotate oppositely, a carrier intermediate said gears and coaxial with said hub, reverse idler pinions on said carrier in mesh with both said coaxial gears, and a reversible power means connected to said carrierto rotate said carrier.

5. In an aircraft propeller structure wherein a propeller hub has a plurality oi propeller blades with their roots rotatable in bearings in said hub, and gear trains in said hub, normally nonrotative with respect to said hub for simultaneously rotating said roots, mechanism for operating said gear trains which comprises a pair of axially spaced gears both coaxial with said hub, gearing connecting one of said coaxial gears to the normally nonrotating gears of said gear trains, gearing including a reverse idler pinion set connecting the other 01' said coaxial gears to the propeller hub, whereby the two coaxial axially spaced gears rotate oppositely, a carrier intermediate said gears and coaxial with said hub, reversing idler pinions on said carrier in mesh with both said coaxial gears, a reverslbleelectric motor connected to said carrier to rotate said carrier,

. a screw adapted to be rotated by rotation of said carrier, and a pitch-indicating carriage intemalwith their roots rotatable in hearings in said hub, and gears trains in said hub, normally nonrotative with respect to said hub for simultaneously rotating said roots, mechanism for operating said gear trains which comprises a pair of axially spaced sears both coaxial with said hub, gearing connecting one of said coaxial gears to the normally nonrotating gears 01' said gear trains, gearing including a reverse idler pinion set connecting the other of said coaxial gears to the propeller hub, whereby the axially spaced coaxial gears rotate oppositely, a carrier intermediate said gears and coaxial with said hub, reversing idler pinions on said carrier in mesh with both said coaxial gears, a reversible electric motor connected to said carrier to rotate said carrier, and a speed-responsive reversing switch for operating said motor in one or the other direction as the speed of the propeller rises or falls.

7. In an aircraft propeller structure wherein a propeller hub has a plurality of propeller blades with their roots rotatable in bearings in said hub, and gear trains in said hub, normally nonrotative with respect to said hub for simultaneously rotating said roots, mechanism for operating said gear trains which comprises a pair of axially spaced gears coaxial with said hub, gearing connecting one of said coaxial gears to the normally nonrotating gears of said gear trains, gearing including a reverse idler pinion set connecting the other of said coaxial gears to the propeller hub, whereby the two coaxial axially spaced gears rotate oppositely, a carrier intermediate said gears and coaxial with said hub, reversing idler pinions on said carrier in mesh with both said coaxial gears, a reversible electric motor connected to said car rier to rotate said carrier, said, motor having "alternate circuits for changing its direction of rotation, a speed-responsive electric switch having a current supply contact and a contact in communication with each motor circuit alternately engageable with the supply contact as the propeller speed rises or fails, a current source, and a manual switch for selectively directing current from said source to said supply contact, to one of source to said supply contact, and limit switches positioned in the path of said carriage and openable thereby at a predetermined pitch increase or decrease.

9. In an aircraft propeller structure wherein a propeller hub has a plurality of propeller blades with their roots rotatable in bearings in said said motor circuits or to the other of said motor circuits.

8. In an aircraft propeller structure wherein a propeller hub has a plurality of propeller b ades with their roots rotatable in bearings in said hub,

and gear trains in said hub, normally nonrotative with respect to said hub for s multaneously rotating said roots, mechanism for operating said gear trains which comprises a pair of axially spaced gears both coaxial with said hub. searing connecting one of said coaxial gears to the normally nonrotating gears of sa d gear trains gearing including a reverse idler pinion set con- I necting the other of said coaxial gears to the propeller hub, whereby the two coaxial axially spaced gears rotate oppositely, a carrier intermediate said gears and coaxial with said hub, reversing idler plnions on said carrier in mesh with both said coaxial gears, a reversible electric motor connected to said carrier to rotate sa d carrier, said motor having alternate circuits for changing its direction of rotation, a screw adapted to be rnhub, and gear trains in said hub, normally nonrotative with respect to said hub for simultaneously rotating said roots, mechanism for operating said gear trains which comprises a pair of axially spaced gears coaxial with said hub, gearing connecting one'oi said axially spaced gears to the normally nonrotating gears 01 said gear trains, gearing including a reverse idler pinion set connecting the other oi said axially spaced gears to the propeller hub, whereby the axially spaced gears rotate oppositely, acarrier intermediate said axially spaced gears and coaxial with said hub, reversing idler pinions on said carrier in mesh with both said axially spaced gears, a reversible electric motor connected to said carrier to rotate said carrier, said motor hav. ing alternate circuits for changing its direction of rotation, a screw adapted to be rotated by rotation of said carrier, and a pitch indicator carriage internally threaded to flt the threads of said screw, 9. current source, a centrifugaliy operable electric switch having an automatic supply contact, with an automatic pitch increase and an automatic pitch decrease contact alternately engageable with the automatic supply contact as the propeller speed respectively rises or falls, a manual switch comprising a manual supply contact, a manual pitch increase contact and a man-r ual pitch decrease contact, with means to selectively connect the current source to the manual supply contact, the manual pitch increase contact or the manual pitch decrease contact, the manual and automatic supply contacts being in electrical communication, four current carrying conductors, two of them joining the automatic and the manual pitch increase contacts to the motor circuit for pitch increase, and the other two joiningthe automatic and the manual pitch decrease contacts to the motor circuit for pitch decrease, and pitch change limiting switches, one in each said current carrying conductor positioned in the path of said carriage so as to be opened thereby at a preselected pitch increase or decrease.

10. An adjustable pitch propeller comprising a hub, a blade having its root rotatable in said hub about the blade axis, a pitch-change gearset in said hub rotatable as a unit with said hub,

individual gears of said gear-set being rotatable relative to said hub, said. gear-set including a driven gear on the blade root, a control gear coaxial with said hub, and intermediate gears between the control gear and the driven gear, adapted, upon relative rotation of said control gear in one direction, with respect to the hub rotation, to rotate the driven gear for pitch increase, and adapted, upon relative rotation of said control gear in the other direction, with respect to hub rotation, to rotate the driven gear for pitch decrease, a diii'erenti'al gear-set comprising two diflerential gears with axes coincident with each other and with the hub axis, a differential carrier rotatable about'said coincident axes. diflerential pinions rotatably carried by said diflerential carrier in mesh with said differential gears, power transmitting means operative upon rotation of said hub in one direction for rotating said differential gears in opposite directions, at least one or said differential gears being drivably connected to said control gear, whereby said difierential carrier remains nonrotative when said control gear rotates as one with said hub, and means to rotate said differential carrier in one or the other direction to provide relative rotation in one or the other direction between said control gear and said hub.

11. An adjustable pitch propeller comprising a hub, a blade having its root rotatable in said hub about the blade axis, a pitch-change gearset in said hub rotatable as a unit with said hub, individual gears of said gear-set being rotatable relative to said hub, saidgear-set including a driven gear on the blade root, a control gear coaxial with said hub, and intermediate gears between the control gear and the driven gear,

.adapted, upon relative rotation of the control gear in one direction, with respect to the hub rotation, to rotate the driven gear for pitch increase, and adapted, upon relative rotation of the control gear in the other direction, with respect to hub rotation, to rotate the driven gear for pitch decrease, a difierential gear-set com-' pinion means, in mesh with both interlacing gears of the second pair, whereby one or the gears of said second pair may be rotated to rotate the other oppositely, sets of pitch changing gearing, each set having one gear on a blade root, said sets operatively connecting the interfacing gears of the second pair'to the blades to the propellers, one set having a higher ratio than the other and so connected to the blade roots that at relatively low pitch the pitch angle of the front and rear blades will be equal, but as a change is made to a higher pitch, the pitch angle of the blades of one hub becomes gradually greater than the pitch angle of the blades of the other hub, and means for rotating one set of the pitch changing gearing while said propeller mechanism is operating.

- 13. In a dual rotation propeller, having two coaxial tandem contrarotating propeller hubs with a plurality of propeller blades in each hubhaving their roots rotatable in bearings in the hubs to change the blade pitch, gear means for imparting rotation to the roots of the blades of one of the hubs to rotate said blades about the prising'two diiierentialgears with axes coincident with each other and coincident withthe hub axis, a differential carrier rotatable, about said coincident axes, difierential pinions rotatably carried by said differential carrier in mesh with said differential gears, two power transmitting means, one drivably connecting the control gear to one differential gear for unitary rotation, and the second drivably connecting the propeller hub to the other differential gear, a reversing gear included in one of said power transmitting means, whereby, upon unitary rotation of said control gear and said hub in one direction, said differential gears rotate at the same speed in opposite directions, whereby said differential car-' rier remains nonrotative whenever said control gear rotates, as one with said hub, and means to rotate said differential carrier in one or the other direction to provide relative rotation in one or the other direction between said control ear and said hub.

12. In an aircraft propeller mechanism having two close coupled coaxial tandem contrarotating propeller hubs with a plurality of propeller blades in each hub having their roots rotatable in bearings in the hubs to change the blade pitch, mechanism for simultaneously rotating the roots of one hub through a slightly greater angle than the roots of the other hub, said mechanism comprising a pair of interfacing gears slightly spaced apart axially, one secured to each hub' for unitary rotation therewith, a second pair of interfacing gears, slightly spaced apart axially and surrounding the first pair, a pinion carrier between the two gears of the first said pair of gears, reversing pinion means on said carrier in mesh with both interfacing gears of the first pair, whereby the carrier is held against free rotation, a second reversing pinion means on said carrier rotatable independently of the first blade axes, and a power transmitting gear train having the driving'gear connected to the blade roots of one hub and the driven gear connected to the blade roots of the other hub, said power transmitting gear train being adapted to rotate the blade roots at the driven end of said gear train through a different pitch angle than the blade roots at the driving end of said gear train.

14. In an aircraft propeller mechanism having two adjacent, coaxial, tandem, contrarotating propeller hubs with a plurality of propeller blades in each hub having their roots rotatable in bearings in said hubs, mechanism for simultaneously rotating the roots to alter the pitch of the blades, said mechanism comprising an external spur gear on each hub secured to rotate therewith, a concentric internal spur gear freely rotatable about each external spur gear, one external spur gear and one internal spur gear constituting a pair of gears, a. pinion carrier between said pairs of gears, a pair of spur pinions rotatable about their axes on said carrier,

a portion of the faces of said spur pinions overlapping and meshing with each other, the remaining portions being extended laterally beyond the carrier and meshed one with each external spur gear, a second pair of spur pinions substantially like the first, except located radially farther from the propeller axis on the carrier and meshed one with each of the internal spur gears, a speed-reducing gear train operatively connecting one of said internal spur gears to the roots of the blades of one propeller, and a second speed reducing gear train operatively connecting the other of said internal spur gears to the roots of the blades of the other propeller, one of said speed reducing gear trains having slightly greater speed reducing capacity than the other.

HOWARD M. MCCOY.

Disclaimer 2,389,161.-Howard M. McCoy, Fairfield, Ohio. CONTROLLABLE PITCH CHANGE MECHANISM FOR DUAL ROTATION PROPELLERS. Patent dated Nov. 20, 1945. Disclaimer filed July 12, 1948, by the inventor. Hereby enters disclaimer to claim 13 of said patent.

[Ojficial Gazette August 10, 1948.] 

